A federal judge in Boston ruled that Spire Corp.‘s Pourchez Retro does not infringe a patent held by Teleflex Medical subsidiary Arrow International.

The Bedford, Mass.-based diversified manufacturer’s Retro product is a hemodialysis catheter used to help clean the blood of patients with impaired kidney function. Arrow alleged that the product infringed its Cannon catheter line.

But Judge Douglas Woodlock of the U.S. District Court for Massachusetts ruled that Arrow’s patent, which it acquired in its 2003 buyout of Diatek Inc., is invalid because the Cannon catheter “is an obvious combination of known elements” because nearly identical catheter designs were already in use when the patent application was filed.

Representatives from Spire and Teleflex did not immediately seek calls returning comment.